Joint operations on Thursday in Australia, the US, Britain, Germany, the Netherlands, Ukraine, Romania and Macedonia led to the websites being closed down.

A 23-year-old man in Stechford, Birmingham, and a 27-year-old man in Tottenham, north London, have been arrested, along with the man in Macedonia.

More arrests are expected.

Soca is also calling on internet service providers to stop individuals registering websites anonymously.

Automated computer programs can register thousands of similar, but different domain names, and it can be difficult to trace them back to their owner.

"Where individuals register domain names for criminal purposes there is a very loose 'know your customer' regime among the website providers," Mr Miles said.

"What we are trying to do is influence the industry to introduce more secure systems so they do know who is registering these sites and they have a more comprehensive customer database, and do more aimed at preventing criminals buying websites and using them for criminal ends," he added.

The BBC's Ben Ando said that, privately, officers admitted that it could be frustrating dealing with internet companies who were not used to being policed and were reluctant to agree to anything that they perceived to be an infringement of their freedoms.